Flow sensing may be used in a variety of different applications. For example, flow sensing may be used in ventilation and respiration machines to detect and control the level of air flow.
Ventilation and respiration machines have been used for many years in hospitals, assisted living quarters, and other locations. These devices are often used to treat respiratory ailments. For example, some individuals suffer from some form of respiratory issue during sleep, such as sleep apnea. Many of these people utilize ventilation and/or respiratory machines to assist in nighttime sleeping. Two types of such machines are a continuous positive airway pressure (CPAP) machine and a variable positive airway pressure (VPAP) machine.
When using these ventilation and/or respiratory machines, it is important to be able to accurately determine the flow rate of ventilation and/or respiration. For example, the air supply pressure from these machines is varied based on whether the person is breathing in or out, such as during inspiration and expiration phases of the respiratory system. By properly controlling the air flow during different phases of breathing, a more comfortable process can result. The more comfortable the ventilation and/or respiratory machine is to a person during use, the more likely the person is to continue to use the ventilation and/or respiratory machine. Users of ventilation and/or respiratory machines may unilaterally decide to cease use of the machine as a result of the machine being uncomfortable during operation, such as when an appropriate air pressure is not supplied.
However, due to the complex nature of breathing and the change in direction and speed of air flow during breathing, it is very difficult to determine flow rates, particularly along a spectrum of different flow levels from a very low flow rate to a very high flow rate.